Napropamide (CASRN 15299-99-7)

Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data, as outlined in the IRIS assessment development process. Sections I (Health Hazard Assessments for Noncarcinogenic Effects) and II (Carcinogenicity Assessment for Lifetime Exposure) present the conclusions that were reached during the assessment development process. Supporting information and explanations of the methods used to derive the values given in IRIS are provided in the guidance documents located on the IRIS website.

STATUS OF DATA FOR Napropamide

File First On-Line 07/01/1989

Category (section)

Status

Last Revised

Oral RfD Assessment (I.A.)

on-line

05/01/1990

Inhalation RfC Assessment (I.B.)

no data

Carcinogenicity Assessment (II.)

no data

_I.
Chronic Health Hazard Assessments for Noncarcinogenic Effects

_I.A.
Reference Dose for Chronic Oral Exposure (RfD)

The oral Reference Dose (RfD) is based on the assumption
that thresholds exist for certain toxic effects such as cellular necrosis.
It is expressed in units of mg/kg-day. In general, the RfD is an estimate
(with uncertainty spanning perhaps an order of magnitude) of a daily exposure
to the human population (including sensitive subgroups) that is likely
to be without an appreciable risk of deleterious effects during a lifetime.
Please refer to the Background Document for an elaboration of these concepts.
RfDs can also be derived for the noncarcinogenic health effects of substances
that are also carcinogens. Therefore, it is essential to refer to other
sources of information concerning the carcinogenicity of this substance.
If the U.S. EPA has evaluated this substance for potential human carcinogenicity,
a summary of that evaluation will be contained in Section II of this file.

__I.A.1.
Oral RfD Summary

Critical Effect

Experimental Doses*

UF

MF

RfD

Decreased body weight
gain in parental
animals and pups

3-Generation Rat
Reproduction Study

Stauffer Chemical Co.,
1978a

NOEL: 30 mg/kg/day

LEL: 100 mg/kg/day

300

1

1E-1mg/kg/day

*Conversion Factors: Actual dose tested

__I.A.2. Principal and Supporting Studies (Oral RfD)

Groups of 15 male and 30 female Charles River CD rats were administered diets
containing 0, 10, 30, or 100 mg/kg/day of napropamide for 3 generations. At
approximately 100 days of age, rats were mated, 1 male with 2 females within
the same treatment group, for 15 consecutive days to produce the F1a litters.
Following weaning of the F1a litters, the F0 female rats were rested for a
minimum of 10 days prior to mating with different partners to the F1b litters.
From the second litter, rats were selected as parents of the next generation.
Feeding of test diet, mating, and production of two litters were repeated with
the F1 rats. From the second F2 litter, rats were selected again to produce
two F3 litters.

The parental NOEL value was 30 mg/kg/day and the parental LEL value was 100
mg/kg/day, based on a decrease in body weight gain in F1 and F2 mothers. The
reproductive NOEL value was 30 mg/kg/day and the reproductive LEL value was
100 mg/kg/day based on a decrease in absolute body weight of F1a, F1b, F2a,
and F3a male and female weanlings.

__I.A.3.
Uncertainty and Modifying Factors (Oral RfD)

UF — An uncertainty factor of 100 was used to account for the inter- and
intraspecies differences. An additional UF of 3 was used to account for the
lack of a chronic feeding study in a second species.

__I.A.5.
Confidence in the Oral RfD

Study — Medium
Database — Medium
RfD — Medium

The critical study is of adequate quality and is given a medium confidence
rating. Since a chronic feeding study in another species is lacking, the data
base is given a medium confidence rating. Medium confidence in the RfD
follows.

__I.A.6.
EPA Documentation and Review of the Oral RfD

Source Document — This assessment is not presented in any existing U.S. EPA
document.

Other EPA Documentation — Pesticide Registration Files

Agency Work Group Review — 04/20/1989

Verification Date — 04/20/1989

Screening-Level Literature Review Findings — A screening-level review conducted by an EPA contractor of the more recent toxicology literature pertinent to the RfD for Napropamide conducted in November 2001 did not identify any critical new studies. IRIS users who know of important new studies may provide that information to the IRIS Hotline at hotline.iris@epa.gov or (202)566-1676.

__I.A.7.
EPA Contacts (Oral RfD)

Please contact the IRIS Hotline for all questions concerning this assessment or IRIS, in general,
at (202)566-1676 (phone), (202)566-1749 (FAX) or hotline.iris@epa.gov
(internet address).

Drinking Water Health Advisories, EPA Regulatory Actions, and
Supplementary Data were removed from IRIS on or before April
1997. IRIS users were directed to the appropriate EPA Program
Offices for this information.